The present invention relates generally to security seals and more particularly to a security seal with dye that provides a visual indication when the seal has been broken. The United States Government has rights in the invention.
Security seals are often used to detect tampering with objects being shipped or stored. In a typical application the object is a container having a moveable cover, door or the like which is secured or locked in a conventional fashion and then sealed. Conventionally, the security seal consists of an elongate portion capable of being threaded through a hole in the object and restrained in place in such a manner that movement of the cover with respect to the container is impossible without removal of the elongate portion of the seal.
A security seal is not usually intended for use as a lock, i.e., it is not designed to withstand a physical assault. The seal is intended to provide an indication of an unauthorized opening of the object under seal. Accordingly, a security seal must be constructed such that it will be deformed when opened, thereby making it difficult to reassemble without leaving any sign of tampering on the seal.
Another feature of a security seal is its ability to be uniquely identified; i.e., its "fingerprint." The function of a seal would be defeated if it could be cut off and subsequently replaced with an identical seal. Accordingly, seals are often stamped with serial numbers or provided with random physical characteristics to make them unique. Although the instant invention is not directed to this feature of a seal, it should be understood that any known fingerprint technique could be utilized with the seals of the invention.
U.S. Pat. No. 3,717,369 to John Stoffel is an example of a typical seal of the plastic padlock type. With this seal, an elongate U-shaped shackle is hinged to a base member at one end and has an irregular shaped surface at the other end. In use, the shackle is placed through the object to be sealed and the irregular end of the shackle fitted into a hole in the base member. The hole contains spring fingers which interact with the irregular surface to prevent the shackle from being withdrawn from the base member without deformation of the seal.
Many other seal systems are described in "Security Seal Handbook" by David Poli, Sandia Laboratories, SAND 78-0440, December 1978 (available from NTIS, Springfield, VA 22161). These seals include crimp/wire, cup/wire, plastic tie, car/plastic, fold/wire, wire hasp padlock, car/box end, car/ball end and cable as types of seals having a pliable elongated member; and bolt and lock as types of seals having a rigid elongated member. The elongate member for each of these seals is a solid piece of plastic or metal.
A method which may be employed to defeat each of the aforementioned seals is to cut and remove the elongate member and then replace it and weld the cut pieces together. Skilled welding and burnishing of the cut pieces can make detection of the unauthorized opening very difficult. This invention overcomes this inherent method of defeat of prior seals.